Citramalic acid and salicylic acid in sugar beet root exudates solubilize soil phosphorus

Abstract

BackgroundIn soils with a low phosphorus (P) supply, sugar beet is known to intake more P than other species such as maize, wheat, or groundnut. We hypothesized that organic compounds exuded by sugar beet roots solubilize soil P and that this exudation is stimulated by P starvation.ResultsRoot exudates were collected from plants grown in hydroponics under low- and high-P availability. Exudate components were separated by HPLC, ionized by electrospray, and detected by mass spectrometry in the range of mass-to-charge ratio (m/z) from 100 to 1000. Eight mass spectrometric signals were enhanced at least 5-fold by low P availability at all harvest times. Among these signals, negative ions with an m/z of 137 and 147 were shown to originate from salicylic acid and citramalic acid. The ability of both compounds to mobilize soil P was demonstrated by incubation of pure substances with Oxisol soil fertilized with calcium phosphate.ConclusionsRoot exudates of sugar beet contain salicylic acid and citramalic acid, the latter of which has rarely been detected in plants so far. Both metabolites solubilize soil P and their exudation by roots is stimulated by P deficiency. These results provide the first assignment of a biological function to citramalic acid of plant origin.

Effect of amending soil with organic acids on perylene uptake into <i>Cucurbita pepo</i>

“…In addition, citramalic acid, which solubilized a small amount of perylene from the soil, has been shown to be present in root exudates of sugar beets and to solubilize soil phosphorus. 17) Again, these findings suggest that citramalic acid also contributes to the solubilization of hydrophobic compounds from the soil and may enhance the uptake of hydrophobic pollutants from the soil by plants.…”

Respuesta de Physalis peruviana L. A la inoculación con bacterias solubilizadoras de fosfato

“…), probablemente diferentes fuentes de carbono asociadas a los exudados radiculares podrían tener un efecto significativo sobre la solubilización de fósforo que sucede en la rizósfera (Liebersbach, 2004). Cinco fuentes adicionales de carbono fueron evaluadas, debido al importante papel que juega en la atracción de los microorganismos a la rizósfera (Walker et al, 2003;Khorassani et al, 2011 Cuadro 1, pueden inferir que la solubilización de fósforo por las bacterias en estudio posiblemente fue influenciada por la fuente de carbono presente. Adicionalmente, las cuatro cepas evaluadas respondieron de manera similar con las diferentes fuentes de carbono utilizadas en el presente estudio; la que estimuló en mayor cantidad la solubilización de fósforo fue el ácido málico, seguido por manitol, sacarosa, glucosa, y ácido glutámico.…”

“…Probably different carbon sources associated with root exudates it could have a significant effect on the solubilization of phosphorus occurs in the rhizosphere (Liebersbach, 2004). Five additional carbon sources were evaluated, due to the important role in attracting the rhizosphere microorganisms (Walker et al, 2003;Khorassani et al, 2011). The results observed in Table 1, may infer that the solubilization of phosphorus by the bacteria under study was possibly influenced by the carbon source.…”

Rhizobacterial salicylate production provokes headaches!

“…Thus, the presence of SA in the rhizosphere must be anticipated. Indeed, SA has been detected in root exudates of for example Arabidopsis (Badri et al 2013), sugar beet (Khorassani et al 2011), sunflower (Park et al 1992) and watermelon (Ling et al 2013). It thus appears that studies on SA in rhizosphere microbiology should not be restricted to SA produced by bacteria.…”